Island fox  (Urocyon littoralis)

Numbers of island foxes declined at alarming rates since 1994, with four of the six subspecies declining by as much as 95 percent. The primary threats causing these devastating declines were predation by golden eagles (Aquila chrysaetos) on the northern Channel Islands, canine distemper virus (CDV) on Santa Catalina Island, and collision with vehicles on San Clemente and San Nicolas Islands (2) (8).

Golden eagles had not always lived on the Channel Islands, but were attracted there by the introduction of wild pigs (Sus scrofa) (9). These impressive birds-of-prey colonized the northern Channel Islands in 1994 and began to prey heavily on foxes, quickly bringing the island fox to the brink of extinction (10). By 1999, only 14 individuals of the San Miguel subspecies remained (11).

On Santa Catalina Island, the introduction of CDV, (believed to be brought to the island by a domestic dog), caused the deaths of about 90 percent of the fox population in just one year, (1999 to 2000) (12). The introduction and spread of CDV, and other canine diseases, remains a potential threat to all the island fox subspecies (8).

In 1999, 32 foxes on San Clemente Island were either culled or permanently removed from the island to zoological institutions, as part of a programme to protect the endangered bird, the loggerhead shrike (Lanius ludovicianus). Another 49 were temporarily held in small pens while the shrikes were nesting, and in 2000, a further 71 foxes were held again. This practice has since been stopped, but the disruption this caused to reproduction and social systems is believed to have significantly affected the San Clemente Island fox population and contributed to its current Critically Endangered status (13).

Like any small, isolated island populations, the island fox remains extremely vulnerable to any catastrophic mortality source, be it predation, canine disease, or environmental extremes (1).

The island fox is listed by the state of California as a threatened species (1), and the islands themselves also receive protection. Santa Rosa, San Miguel and Santa Cruz are part of the Channel Islands National Park, which is protected by the U.S National Park Service, and the western portion of Santa Cruz Island is also protected by The Nature Conservancy. Dogs and cats are prohibited from being brought into the Channel Islands National Park, in order to prevent infections from being transmitted to the foxes (6). Santa Catalina Island is owned and managed by the Catalina Island Conservancy (14), and the remaining two islands, San Nicolas and San Clemente, are owned and managed by the U.S. Navy (1).

Captive breeding and reintroduction programmes on San Miguel, Santa Rosa and Santa Cruz Islands, along with programmes to remove and relocate golden eagles and reintroduce bald eagles, have been a remarkable success. The San Miguel population, which was once the most endangered, made such a strong recovery through the captive breeding program, and the wild population was doing so well, that all releasable individuals were returned to the wild in July 2007. On Santa Cruz, many captive bred foxes have also been returned to the wild. Unfortunately, a number of these have been the victims of continued golden eagle predation, but with January 2007 seeing the removal of all the feral pigs, it is hoped that there will be less motivation for any golden eagles to remain on the island (11).

On Santa Catalina, less than one year after the CDV-caused decline in the fox population, the Institute for Wildlife Studies began an island-wide vaccination program against this disease. In addition, a captive breeding program was initiated to aid in repopulating the island. The program has been a resounding success (12), and the population continues to recover from its near-catastrophic decline (11). With the continuation of such determined conservation efforts, hopefully the island fox will one day serve as an example of how critically endangered species can be pulled back from the brink of extinction.